Conductive film and transparent heating element

ABSTRACT

Provided is a conductive film suitable for use in a transparent heating element having superior visibility and heat generation properties. A conductor of a first conductive film has a mesh pattern which has a plurality of lattice cross points (intersections) formed by a plurality of first metal nanowires and a plurality of second metal nanowires. The conductor between intersections is formed in a wave-like shape having at least one curve. The array period of an arc of one first metal nanowire from among parallel adjacent first metal nanowires is one period. The array period of an arc of another first metal nanowire constitutes two periods. Similarly, the array period of an arc of one second metal nanowire is one period. The array period of an arc of another second metal nanowire constitutes two periods.

TECHNICAL FIELD

The present invention relates to a conductive film that can be used as apart of a defroster (defrosting device) or a window glass for a vehicle,as a heating sheet for heat generation by applying electric current, oras an electrode for a touch panel, an inorganic EL device, an organic ELdevice, or a solar cell, and to a transparent heating element containingthe conductive film.

BACKGROUND ART

A device described in Japanese Laid-Open Patent Publication No.2005-197234 has recently been proposed as an electroluminescence devicecapable of large-area (e.g., 0.25 m² or more) light emission with highluminance and long lifetime.

Meanwhile, structures described in Japanese Laid-Open Patent PublicationNos. 2007-026989 and 10-289602 have been known as a vehicle lightcontaining a conductive film capable of preventing illuminance reductionof the light.

The illuminance of a vehicle light may be reduced due to the followingcauses:

(1) adhesion and accumulation of snow on the circumferential surface ofthe front cover,

(2) adhesion and freezing of rain water or car wash water on thecircumferential surface of the front cover, and

(3) progression of (1) and (2) due to use of an HID lamp light sourcehaving a high light intensity even under low power consumption (a smallheat generation amount).

The structure described in Japanese Laid-Open Patent Publication No.2007-026989 is obtained by attaching a heating element containing atransparent insulating sheet and a conductive pattern printed thereon toa formed lens using an in-mold method. Specifically, the conductivepattern of the heating element is composed of a composition containing anoble metal powder and a solvent-soluble thermoplastic resin.

The structure described in Japanese Laid-Open Patent Publication No.10-289602 is obtained by attaching a heating element to a lens portionin the vehicle lamp. The lens portion is heated by applying an electricfield to the heating element under a predetermined condition. Thedocument describes that the heating element comprises a transparentconductive film of ITO (Indium Tin Oxide), etc.

Furthermore, a device described in Japanese Laid-Open Patent PublicationNo. 2006-190585 has been proposed as a dye-sensitized solar cell capableof reducing adverse effects of reflected electromagnetic waves withoutsignificant reduction of the power generation efficiency. In addition,in the field of electromagnetic-shielding films, Japanese Laid-OpenPatent Publication No. 2004-221565 has disclosed a technology forlimiting a thickening ratio of line intersections in a mesh to minimizePDP image quality deterioration due to moire or the like.

SUMMARY OF INVENTION

In the heating element described in Japanese Laid-Open PatentPublication No. 2007-026989, one conductive wire may be arranged in azigzag manner on a headlamp front cover or the like to form a longconductive line in view of obtaining a desired resistance value (e.g.,about 40 ohm). However, a potential difference may be disadvantageouslygenerated between adjacent conductive line portions to cause migration.

In the heating element described in Japanese Laid-Open PatentPublication No. 10-289602, the transparent conductive film of ITO, etc.is used. The film cannot be formed on a curved surface of a formed bodyby a method other than vacuum sputtering methods. Thus, the heatingelement is disadvantageous in efficiency, cost, etc.

In addition, since the transparent conductive film is composed of aceramic such as ITO, the film may be cracked when bent in an in-moldmethod. Therefore, the film can hardly be used in a vehicle light frontcover or the like having the curved-surface body and the transparentheater though it can be used in a window glass with relatively lesscurved surface.

Thus, the conventional heating elements are less versatile andexclusively used in a vehicle light front cover, a window glass, etc.

In the case of using a conductive film as an electrode of a touch panel,an inorganic EL device, or an organic EL device, a conductive portionhas to be formed in view of light refraction and diffraction in theportion to prevent glare caused by a backlight, etc.

The solar cell described in Japanese Laid-Open Patent Publication No.2006-190585 utilizes a transparent conductive film of ITO, etc., therebyresulting in the same problems as Japanese Laid-Open Patent PublicationNo. 10-289602. Also the electromagnetic-shielding film technologydescribed in Japanese Laid-Open Patent Publication No. 2004-221565 stillhas room for improvement.

Under such circumstances, an object of the present invention is toprovide a conductive film and a transparent heating element usable as aheating sheet for heat generation by applying electric current, whichcan exhibit an improved heat generation efficiency, can prevent glarecaused by a vehicle or outdoor light, and can be versatilely used in avehicle light front cover, a window glass, etc.

Another object of the present invention is to provide a conductive filmthat can be used as an electrode of a touch panel, an inorganic ELdevice, or an organic EL device to prevent glare or the like caused by abacklight.

A further object of the present invention is to provide a conductivefilm that can be used as an electrode of a solar cell to shieldelectromagnetic waves and to lower the surface resistance withoutreduction of the power generation efficiency.

For the purpose of realizing a highly versatile transparent heatingelement usable for a vehicle light front cover, a building window glass,a vehicle window glass, etc., the inventor has examined a conductivefilm according to a comparative example having a plurality of conductiveportions and a plurality of opening portions, which provide mesh shapesin combination. Specifically, the conductive portions are formed in astraight line shape and are crossed to form the mesh shapes.

When the heating wire is arranged in a zigzag manner in the conventionalstructure, a potential difference is generated between the adjacentconductive line portions to cause migration disadvantageously. Incontrast, when the conductive portions are formed in the mesh shapes,the adjacent conductive portions are intrinsically in the short circuitcondition, and the migration is never a problem.

The conductive portions can be composed of a thin metal wire or the likeexcellent in malleability and ductility, and therefore can be formedalong a three-dimensional curved surface having a minimum curvatureradius of 300 mm or less.

However, it has been found that in the conductive film according to thecomparative example, diffracted lights generated in the ends of thestraight conductive portions interact with each other in diffractionpoints arranged linearly on the intersections to emit an intenseinterfering light. Also on the conductive portions, diffraction pointsare arranged linearly to emit an intense light, though the light isweaker than the interfering light from the intersections. Therefore,when the conductive film is incorporated in a window glass, significantglare or the like is disadvantageously caused due to the interference ofthe diffracted lights.

Thus, in the present invention, the problem has been solved by using thefollowing structure.

[1] A conductive film according to a first aspect of the presentinvention comprising a plurality of conductive portions and a pluralityof opening portions, wherein the combination of the conductive portionsand the opening portions has mesh shapes, the conductive portions areformed of a plurality of conductive thin metal wires in a mesh patternhaving a plurality of lattice intersections, and some of the conductivethin metal wires are formed in a wavy line shape containing arcsextending in alternate directions, at least one of the arcs beingdisposed between the intersections.

In this structure, diffraction points are not arranged linearly on theintersections of the conductive portions not having a straight section,and an interfering light from the intersections has a low intensity. Thesame phenomenon is caused on the conductive portions, and also aninterfering light from the conductive portions has a low intensity. Inthe present invention, the mesh shapes can reduce glare or the likecaused by the interference of the diffracted lights. Therefore, theconductive film is suitable for a transparent heating element to beincorporated in a window glass (such as a building window glass or avehicle window glass), a vehicle light front cover, etc. The straightsection may be appropriately formed if necessary depending on theproduct using the conductive film (such as the window glass or thevehicle light front cover), the period or amplitude of the wavy lineshape, etc.

Furthermore, when the conductive film of the present invention is usedas an electrode of a touch panel, an inorganic EL device, or an organicEL device, the conductive film can prevent glare or the like caused by abacklight and thus visibility deterioration of a displayed image.

Furthermore, when the conductive film is used as an electrode of a solarcell, the conductive film can act as an electromagnetic-shielding filmand can exhibit a low surface resistance to prevent reduction of powergeneration efficiency.

[2] A conductive film according to the first aspect, wherein the meshpattern is formed by crossing a plurality of first thin metal wiresarranged in one direction and a plurality of second thin metal wiresarranged in another direction.

[3] A conductive film according to the first aspect, wherein the arcshave a central angle of 75° to 105° (preferably approximately 90°).

[4] A conductive film according to the first aspect, wherein at leastthe first thin metal wires are formed in wavy line shapes containing atleast one curve between the intersections, and the wavy line shapes ofadjacent parallel first thin metal wires have different periods.

[5] A conductive film according to the first aspect, wherein amongadjacent parallel first thin metal wires, one first thin metal wire isformed in a straight line shape, and the other first thin metal wire isformed in a wavy line shape containing at least one curve between theintersections.

[6] A conductive film according to the first aspect, wherein the secondthin metal wires are formed in wavy line shapes containing at least onecurve between the intersections, and the wavy line shapes of adjacentparallel second thin metal wires have different periods.

[7] A conductive film according to the first aspect, wherein amongadjacent parallel second thin metal wires, one second thin metal wire isformed in a straight line shape, and the other second thin metal wire isformed in a wavy line shape containing at least one curve between theintersections.

[8] A conductive film according to the first aspect, wherein the arcshave a central angle of 90°, and the number of the arcs on thecircumference line of each mesh shape is 2k (k=1, 2, 3, . . . ).

[9] A conductive film according to the first aspect, wherein the arcshave a central angle of 90°, and the number of the arcs on thecircumference line of each mesh shape is 4k (k=1, 2, 3, . . . ).

[10] A conductive film according to the first aspect, wherein in a lineconnecting the central points of optional adjacent two mesh shapesdisposed along the arrangement of the intersections of the conductiveportions, the length of a first line segment connecting the centralpoint of one mesh shape and the intersection is equal to the length of asecond line segment connecting the central point of the other mesh shapeand the intersection.

[11] A conductive film according to the first aspect, wherein in a lineconnecting the central points of optional adjacent two mesh shapesdisposed along the extending direction of one conductive portion, thelength of a third line segment connecting the central point of one meshshape and another conductive portion is equal to the length of a fourthline segment connecting the central point of the other mesh shape andthe other conductive portion.

[12] A conductive film according to the first aspect, wherein at leastone of a pattern of the first thin metal wires a pattern of the secondthin metal wires is set such that, calling one thin metal wire having asmallest arrangement period number of the arcs a number-one first thinmetal wire, the arrangement period number of the arcs is increasedstepwise from the number-one thin metal wire to another thin metal wirearranged in one direction.

[13] A conductive film according to the first aspect, wherein at leastone of a pattern of the first thin metal wires and a pattern of thesecond thin metal wires is set such that two thin metal wires disposedadjacently on either side of a thin metal wire having a smallestarrangement period number of the arcs have approximately the samearrangement period numbers of the arcs, and two thin metal wiresdisposed adjacently on either side of a thin metal wire having a largestarrangement period number of the arcs have approximately the samearrangement period numbers of the arcs.

[14] A conductive film according to the first aspect, wherein theconductive portions have a crossing angle of approximately 90° in theintersections.

[15] A conductive film according to the first aspect, wherein theconductive portions contain a metallic silver portion formed by exposingand developing a photosensitive silver salt layer disposed on atransparent support.

[16] A transparent heating element according to a second aspect of thepresent invention comprising a conductive film according to the firstaspect.

As described above, when the conductive film or the transparent heatingelement of the present invention is used as a heating sheet for heatgeneration by applying electric current, it can exhibit an improved heatgeneration efficiency, can prevent glare caused by a vehicle or outdoorlight, and can be versatilely used in a vehicle light front cover, awindow glass, etc.

When the conductive film of the present invention is used as anelectrode of a touch panel, an inorganic EL device, or an organic ELdevice, glare or the like caused by a backlight can be prevented.

When the conductive film of the present invention is used as anelectrode of a solar cell, it can act as an electromagnetic-shieldingfilm and can exhibit a low surface resistance to prevent reduction ofthe power generation efficiency.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a plan view partially showing a first conductive film;

FIG. 2 is a cross-sectional view taken along the II-II line of FIG. 1;

FIG. 3 is a plan view showing an example structure of a transparentheating element using the first conductive film;

FIG. 4 is an explanatory view schematically showing a mesh pattern ofthe first conductive film;

FIG. 5 is a front view showing a product using the first conductive film(a first conductive sheet);

FIG. 6 is a back view showing the first conductive sheet;

FIG. 7 is a top view showing the first conductive sheet;

FIG. 8 is a bottom view showing the first conductive sheet;

FIG. 9 is a left side view showing the first conductive sheet;

FIG. 10 is a right side view showing the first conductive sheet;

FIG. 11 is a perspective view showing the first conductive sheet;

FIG. 12 is a front view showing the use of the first conductive sheet;

FIG. 13 is a partially-omitted plan view showing a second conductivefilm;

FIG. 14 is an explanatory view schematically showing a mesh pattern of athird conductive film;

FIG. 15 is a front view showing a product (a conductive sheet) using thethird conductive film (a second conductive sheet);

FIG. 16 is a back view showing the second conductive sheet;

FIG. 17 is a top view showing the second conductive sheet;

FIG. 18 is a bottom view showing the second conductive sheet;

FIG. 19 is a left side view showing the second conductive sheet;

FIG. 20 is a right side view showing the second conductive sheet;

FIG. 21 is a perspective view showing the second conductive sheet;

FIG. 22 is a front view showing the use of the second conductive sheet;

FIG. 23 is an explanatory view schematically showing a mesh pattern of afourth conductive film;

FIG. 24 is an explanatory view schematically showing a mesh pattern of afifth conductive film;

FIG. 25 is an explanatory view schematically showing a mesh pattern of asixth conductive film;

FIG. 26 is an explanatory view schematically showing a mesh pattern of aseventh conductive film;

FIG. 27 is an explanatory view schematically showing a mesh pattern ofan eighth conductive film;

FIGS. 28A to 28E are views showing the process of a first productionmethod for producing a conductive film according to an embodiment of thepresent invention;

FIGS. 29A and 29B are views showing the process of a second productionmethod for producing the conductive film of the embodiment;

FIGS. 30A and 30B are views showing the process of a third productionmethod for producing the conductive film of the embodiment; and

FIG. 31 is a view showing the process of a fourth production method forproducing the conductive film of the embodiment.

DESCRIPTION OF EMBODIMENTS

Several embodiments of the conductive film and the transparent heatingelement of the present invention will be described below with referenceto FIGS. 1 to 31.

As shown in FIG. 1, a conductive film according to a first embodiment(hereinafter referred to as the first conductive film 10A) contains aplurality of conductive portions 12 and a plurality of opening portions14, and the combination of the conductive portions 12 and the openingportions 14 has mesh shapes M. Each mesh shape M is a combined shape ofone opening portion 14 and four conductive portions 12 surrounding theopening portion 14.

The first conductive film 10A can be used as a part of a defroster(defrosting device) or a window glass for a vehicle. The firstconductive film 10A can be used also in a transparent heating elementcapable of heat generation by applying electric current. As shown inFIG. 2, the first conductive film 10A has a transparent film substrate16, and the conductive portions 12 and the opening portions 14 formedthereon. As shown in FIG. 3, when the first conductive film 10A is usedin a transparent heating element 18, a first electrode 20 a and a secondelectrode 20 b are disposed on the opposite ends of the first conductivefilm 10A (e.g., the right and left ends of FIG. 3). When an electriccurrent is flowed from the first electrode 20 a to the second electrode20 b, the transparent heating element 18 generates heat. Thus, a heatingobject (such as a building window glass, a vehicle window glass, or avehicle light front cover), which is brought into contact or equippedwith the transparent heating element 18, is heated. As a result, snow orthe like attached to the object can be removed.

As shown in FIG. 1, the conductive portions 12 in the first conductivefilm 10A have a mesh pattern 22 formed by crossing a plurality of firstthin metal wires 12 a arranged at a first pitch L1 in one direction (thex direction of FIG. 1) and a plurality of second thin metal wires 12 barranged at a second pitch L2 in another direction (the y direction ofFIG. 1). The first pitch L1 and the second pitch L2 may be selectedwithin a range of 150 μm to 6000 μm (6.0 mm). The line width d of thefirst thin metal wires 12 a and the second thin metal wires 12 b may beselected within a range of 5 μm to 200 μm (0.2 mm). It is to beunderstood that the line width d may be selected within a range of 5 to50 μm to improve the transparency.

Thus, the conductive portions 12 are formed of the plural first thinmetal wires 12 a and the plural second thin metal wires 12 b in the meshpattern 22 having a large number of lattice intersection points(intersections 24). Each of the conductive portions 12 is formed in awavy line shape containing at least one curve between the intersections24.

Specifically, among the plural first thin metal wires 12 a, eachalternate first thin metal wire 12 a 1 (one first thin metal wire 12 a1) has a shape with arc-shaped curves, and two arcs 26 extending inalternate crest and trough directions are continuously formed betweenthe intersections 24. Among the plural first thin metal wires 12 a, eachfirst thin metal wire 12 a 2 other than the first thin metal wires 12 a1 (the other first thin metal wire 12 a 2) has a shape with arc-shapedcurves, and four arcs 26 extending in alternate crest and troughdirections are continuously formed between the intersections 24.

In terms of the arrangement period of the arcs 26, the length, in whichtwo arcs 26 extending in alternate crest and trough directions arecontinuously formed, is considered as 1 period. Then, the one first thinmetal wire 12 a 1 have 1 period of the arcs between the intersections,and the other first thin metal wires 12 a 2 have 2 periods of the arcsbetween the intersections.

Thus, in the first conductive film 10A, the adjacent parallel first thinmetal wires 12 a (the one first thin metal wire 12 a 1 and the otherfirst thin metal wire 12 a 2) have different arc arrangement periods.

Also among the second thin metal wires 12 b, one second thin metal wires12 b 1 have 1 period of the arcs between the intersections 24, and theother second thin metal wires 12 b 2 have 2 periods of the arcs betweenthe intersections 24.

It is to be understood that, when the one first thin metal wire 12 a 1has i period of the arcs between the intersections 24, the other firstthin metal wire 12 a 2 has j period of the arcs between theintersections 24, the one second thin metal wire 12 b 1 has p period ofthe arcs between the intersections 24, and the other second thin metalwire 12 b 2 has q period of the arcs between the intersections 24, theperiods may satisfy one of the following relations.

(1) i≠j, i=p, j=q

(2) i≠j, i≠p, j=q, p≠q

(3) i≠j, i=p, j≠q, p≠q

(4) i≠j, i≠p, j≠q, p≠q

Each arc 26 has a central angle of 75° to 105°, preferably approximately90°. The conductive portions 12 have a crossing angle of approximately90°. Though the preferred central angle and the preferred crossing angleare represented by the term “approximately 90°” in view of productiontolerance, it is desired that the central angle and the crossing angleare ideally 90°. The 1 period is preferably 50 to 2000 μm.

The wavy line shape of each conductive portion 12 has a constantamplitude h. When an imaginary line 28 connects two adjacentintersections 24 and a line perpendicular to the imaginary line 28extends from a crest of the wavy line shape, the amplitude h is adistance from the crest to the intersection point of the perpendicularline and the imaginary line 28. The amplitude h is preferably 10 to 500μm. Though the conductive portion 12 has the wavy line shape with theconstant amplitude h in this embodiment, adjacent two arcs 26 betweenthe intersections 24 may have different amplitudes, and the adjacentparallel wavy line shapes may have different arc amplitudes.

As schematically shown in FIG. 4, in the first conductive film 10A, in aline connecting the central points C1 and C2 of optional adjacent twomesh shapes M1 and M2 disposed along the arrangement of theintersections 24, the length La of a first line segment connecting thecentral point of one mesh shape M1 and the intersection 24 is equal tothe length Lb of a second line segment connecting the central point ofthe other mesh shape M2 and the intersection 24.

Furthermore, as shown in FIG. 4, in a line connecting the central pointsC3 and C4 of optional adjacent two mesh shapes M3 and M4 disposed alongthe extending direction of the second thin metal wire 12 b, the lengthLc of a third line segment connecting the central point C3 of one meshshape M3 and the first thin metal wire 12 a is equal to the length Ld ofa fourth line segment connecting the central point C4 of the other meshshape M4 and the first thin metal wire 12 a.

The first conductive film 10A has a total light transmittance of 70% ormore but less than 99%, which can be increased to 80% or more or 85% ormore.

Thus, in the first conductive film 10A, the conductive portions 12hardly have a straight section, so that diffraction points are notarranged linearly on the intersections 24 of the conductive portions 12.In addition, the adjacent parallel thin metal wires are formed in thewavy line shapes with different periods, whereby the diffraction pointsare discretely distributed to further reduce glare or the like caused byinterference of diffracted lights.

Thus, an interfering light from the intersections 24 has a lowintensity, and also an interfering light from the conductive portions 12has a low intensity. The glare or the like caused by the interference ofdiffracted lights is thus prevented that would otherwise be caused bythe mesh shapes.

Furthermore, since the first thin metal wires 12 a are arranged at thefirst pitch L1 and the second thin metal wires 12 b are arranged at thesecond pitch L2 in the first conductive film 10A, the opening portions14 have approximately constant opening areas, whereby the glare or thelike caused by the interference of diffracted lights can be prevented onthe whole surface, and significant glare or the like is not causedlocally.

Therefore, the first conductive film 10A is suitable for the transparentheating element 18, which can be incorporated in a window glass (such asa building window glass or a vehicle window glass), a vehicle lightfront cover, etc. The straight section may be appropriately formed inthe wavy line shape if necessary depending on the product (such as thewindow glass or the vehicle light front cover), the period or amplitudeof the wavy line shape, etc. The wavy line shape may be a sine wavecurve shape.

In the first conductive film 10A, the number of the arcs 26 on thecircumference line of one mesh shape M is 4k (k=1, 2, 3, . . . ).Therefore, the first conductive film 10A is capable of exhibiting a lowoverall surface resistance, improving heat generation efficiency in atransparent heating element, and improving power generation efficiencyin a solar cell.

An example of a product such as a conductive sheet (hereinafter referredto as the first conductive sheet 100) using the first conductive film10A will be described below with reference to also FIGS. 5 to 12. FIG. 5is a front view showing the first conductive sheet 100, FIG. 6 is a backview showing the first conductive sheet 100, FIG. 7 is a top viewshowing the first conductive sheet 100, FIG. 8 is a bottom view showingthe first conductive sheet 100, FIG. 9 is a left side view showing thefirst conductive sheet 100, and FIG. 10 is a right side view showing thefirst conductive sheet 100. Further, FIG. 11 is a perspective viewshowing the first conductive sheet 100, and FIG. 12 is a front viewshowing the use of the first conductive sheet 100.

The first conductive sheet 100 contains a transparent film substrate 16and a wavy conductive pattern (conductive portions) 12 formed thereon.The design of the first conductive sheet 100 is continuously formed inthe vertical and horizontal directions of the front view. In the firstconductive sheet 100, the transparent film substrate 16 is colorless andclear, and the conductive pattern (conductive portions) 12 has a blackcolor.

The first conductive sheet 100 can be used as a part of a defroster(defrosting device) or a window glass for a vehicle, etc. The firstconductive sheet 100 can be used also as a heating sheet capable of heatgeneration by applying electric current. Furthermore, the firstconductive sheet 100 can be used as an electrode for a touch panel, aninorganic EL device, an organic EL device, or a solar cell. For example,electrodes are disposed on the opposite ends of the first conductivesheet 100 (e.g., the right and left ends of FIG. 12), and an electriccurrent is flowed from one electrode to the other electrode to heat theconductive pattern 12. Thus, a heating object such as a vehicleheadlight covered with snow, which is brought into contact or equippedwith the first conductive sheet 100, is heated. As a result, the snowcan be melted and removed from the headlight. The pitches of theconductive pattern 12 (the dimensions L1 and L2 of FIG. 5) may beselected within a range of 0.1 to 6.0 mm (more preferably 0.3 to 6.0mm). In this example, the dimensions L1 and L2 are the same value ofabout 5.8 mm. The line width of the conductive pattern 12 (the dimensiond of FIG. 5) is about 0.1 mm in this example though it may be selectedwithin a range of 0.01 to 0.2 mm. The thickness of the transparent filmsubstrate 16 (the dimension t2 of FIG. 8) is about 0.6 mm in thisexample though it may be selected within a range of 0.01 to 2.0 mm. Thethickness of the conductive pattern 12 (the dimension t1 of FIG. 8) isabout 0.1 mm in this example though it may be selected within a range of0.001 to 0.2 mm.

A conductive film according to a second embodiment (hereinafter referredto as the second conductive film 10B) will be described below withreference to FIG. 13.

As shown in FIG. 13, the structure of the second conductive film 10B isapproximately the same as that of the above first conductive film 10A,but different in the following respect.

Thus, in the second conductive film 10B, among adjacent parallel firstthin metal wires 12 a 1 and 12 a 2, one first thin metal wire 12 a 1 isformed in a wavy line shape containing at least one curve (e.g., the arc26) between the intersections 24, and the other first thin metal wire 12a 2 is formed in a straight line shape.

Similarly, among adjacent parallel second thin metal wires 12 b 1 and 12b 2, one second thin metal wire 12 b 1 is formed in a wavy line shapecontaining at least one curve (e.g., the arc 26) between theintersections 24, and the other second thin metal wire 12 b 2 is formedin a straight line shape.

It should be noted that the wavy line shapes of the one first thin metalwire 12 a 1 and the one second thin metal wire 12 b 1 have 1 period ofthe arcs 26 between the intersections 24.

Though not shown in the drawing, when the second conductive film 10B isused in a transparent heating element 18, first and second electrodesare disposed on the opposite ends of the second conductive film 10B.When an electric current is flowed from the first electrode to thesecond electrode, the transparent heating element 18 generates heat.

Thus, in the second conductive film 10B, diffraction points are notarranged linearly on the intersections 24 of the conductive portions 12not having a straight section, whereby the mesh shapes can prevent theglare or the like caused by the interference of the diffracted lights.

Therefore, the second conductive film 10B is suitable for thetransparent heating element 18 that can be incorporated in a windowglass (such as a building window glass or a vehicle window glass), avehicle light front cover, etc. Though the first thin metal wires 12 aare arranged at the first pitch L1 in one direction and the second thinmetal wires 12 b are arranged at the second pitch L2 in the otherdirection in the above first conductive film 10A and the secondconductive film 10B, the pitches may be increased or decreased locally.Thus, the opening areas of the opening portions 14 may be locallychanged. A local portion having a decreased pitch (an opening portion 14with a smaller opening area) exhibits higher heat generation efficiency,and a local portion having an increased pitch (an opening portion 14with a larger opening area) exhibits a higher light transmittance. Inthe case of using the transparent heating element 18 in a window glass,the pitches may be selected in each portion of the window glass such asa portion requiring rapid snow melting or a portion requiringtransparency. Particularly, when the transparent heating element 18 isused in a vehicle window glass (a front window glass), the rapid snowmelting, the transparency, and a longer current pathway are required ina portion facing a driver, so that it is preferred that the localportion with an increased pitch and the local portion with a decreasedpitch are arranged in combination.

A conductive film according to a third embodiment (hereinafter referredto as the third conductive film 10C) will be described below withreference to FIG. 14.

As schematically shown in FIG. 14, the structure of the third conductivefilm 10C is approximately the same as that of the above first conductivefilm 10A, but different in the following respect.

Thus, for example, in the first thin metal wires 12 a, a number-onefirst thin metal wire 12 a(1) has a smallest arrangement period numberof the arcs 26 (a largest length of the arrangement period of the arcs26), and the arrangement period number of the arcs 26 is increasedstepwise (the length of the arc arrangement period is reduced stepwise)from the number-one first thin metal wire 12 a(1) to another first thinmetal wire 12 a arranged in one direction. In the example of FIG. 14,the number-one first thin metal wire 12 a(1) has an arc arrangementperiod number of 1, the number-two first thin metal wire 12 a(2)adjacent to the number-one first thin metal wire 12 a(1) in the onedirection has an arc arrangement period number of 2, and thenumber-three first thin metal wire 12 a(3) adjacent to the number-twofirst thin metal wire 12 a(2) in the one direction has an arcarrangement period number of 3. The combinations of the wires arearranged in the one direction. The first thin metal wire 12 a adjacentto the number-one first thin metal wire 12 a(1) in the oppositedirection has an arc arrangement period number of 3. Therefore, thefirst thin metal wire 12 a having the largest arc arrangement periodnumber is adjacent to the first thin metal wire 12 a having the smallestarc arrangement period number. The second thin metal wires 12 b arearranged in the same manner.

Also in the third conductive film 10C, the conductive portions 12 hardlyhave a straight section, so that diffraction points are not arrangedlinearly on the intersections 24 of the conductive portions 12. Inaddition, the adjacent parallel thin metal wires 12 are formed in thewavy line shapes with different periods, whereby the diffraction pointsare discretely distributed to further reduce the glare or the likecaused by the interference of diffracted lights.

The number of the arcs 26 on the circumference line of one mesh shape Mis 2k (k=1, 2, 3, . . . ). Therefore, though the surface resistancelowering effect of the third conductive film 10C is lower than that ofthe first conductive film 10A having the number 4k, the third conductivefilm 10C is capable of improving heat generation efficiency in atransparent heating element and improving power generation efficiency ina solar cell.

An example of a product such as a conductive sheet (hereinafter referredto as the second conductive sheet 200) using the third conductive film10C will be described below with reference also to FIGS. 15 to 22. FIG.15 is a front view showing the second conductive sheet 200, FIG. 16 is aback view showing the second conductive sheet 200, FIG. 17 is a top viewshowing the second conductive sheet 200, FIG. 18 is a bottom viewshowing the second conductive sheet 200, FIG. 19 is a left side viewshowing the second conductive sheet 200, and FIG. 20 is a right sideview showing the second conductive sheet 200. Further, FIG. 21 is aperspective view showing the second conductive sheet 200, and FIG. 22 isa front view showing the use of the second conductive sheet 200.

The second conductive sheet 200 contains a transparent film substrate 16and a wavy conductive pattern (conductive portions) 12 formed thereon.The design of the second conductive sheet 200 is continuously formed inthe vertical and horizontal directions of the front view. In the secondconductive sheet 200, the transparent film substrate 16 is colorless andclear, and the conductive pattern (conductive portions) 12 has a blackcolor.

The second conductive sheet 200 can be used as a part of a defroster(defrosting device) or a window glass for a vehicle, etc. The secondconductive sheet 200 can be used also as a heating sheet capable of heatgeneration by applying electric current. Furthermore, the secondconductive sheet 200 can be used as an electrode for a touch panel, aninorganic EL device, an organic EL device, or a solar cell. For example,electrodes are disposed on the opposite ends of the second conductivesheet 200 (e.g., the right and left ends of FIG. 22), and an electriccurrent is flowed from one electrode to the other electrode to heat theconductive pattern 12. Thus, a heating object such as a vehicleheadlight covered with snow, which is brought into contact or equippedwith the second conductive sheet 200, is heated. As a result, the snowcan be melted and removed from the headlight. The pitches of theconductive pattern 12 (the dimensions L1 and L2 of FIG. 15) may beselected within a range of 0.15 to 6.0 mm. In this example, thedimensions L1 and L2 are the same value of about 5.8 mm. The line widthof the conductive pattern 12 (the dimension d of FIG. 15) is about 0.1mm in this example though it may be selected within a range of 0.01 to0.2 mm. The thickness of the transparent film substrate 16 (thedimension t2 of FIG. 18) is about 0.6 mm in this example though it maybe selected within a range of 0.01 to 2.0 mm. The thickness of theconductive pattern 12 (the dimension t1 of FIG. 18) is about 0.1 mm inthis example though it may be selected within a range of 0.001 to 0.2mm.

A conductive film according to a fourth embodiment (hereinafter referredto as the fourth conductive film 10D) will be described below withreference to FIG. 23.

As schematically shown in FIG. 23, the structure of the fourthconductive film 10D is approximately the same as that of the above thirdconductive film 10C, but different in the following respect.

Thus, for example, in the first thin metal wires 12 a, two first thinmetal wires 12 a disposed adjacently on either side of a first thinmetal wire 12 a having a smallest arc arrangement period number (alargest arc arrangement period length) have the same arc arrangementperiod number, and two first thin metal wires 12 a disposed adjacentlyon either side of a first thin metal wire 12 a having a largest arcarrangement period number (a smallest arc arrangement period length)have the same arc arrangement period number. The second thin metal wires12 b are formed in the same manner.

Also in the fourth conductive film 10D, the conductive portions 12hardly have a straight section, so that diffraction points are notarranged linearly on the intersections 24 of the conductive portions 12.In addition, the adjacent parallel thin metal wires 12 are formed in thewavy line shapes with different periods, whereby the diffraction pointsare discretely distributed to further reduce the glare or the likecaused by the interference of diffracted lights.

In the fourth conductive film 10D, the number of the arcs 26 on thecircumference line of one mesh shape M is 4k (k=1, 2, 3, . . . ).Therefore, the fourth conductive film 10D is capable of improving heatgeneration efficiency in a transparent heating element and improvingpower generation efficiency in a solar cell.

Though not shown in the drawings, for example, the pattern of the firstthin metal wires 12 a may be arranged such that, calling one first thinmetal wire 12 a having a smallest arc arrangement period number anumber-one first thin metal wire 12 a, the arc arrangement period numberof the first thin metal wire 12 a is increased stepwise from thenumber-one first thin metal wire 12 a in one direction in the samemanner as in the third conductive film 10C, and the pattern of thesecond thin metal wires 12 b may be arranged such that two second thinmetal wires 12 b disposed adjacently on either side of a second thinmetal wire 12 b having a smallest arc arrangement period number have thesame arc arrangement period number and two second thin metal wires 12 bdisposed adjacently on either side of a second thin metal wire 12 bhaving a largest arc arrangement period number have the same arcarrangement period number in the same manner as in the fourth conductivefilm 10D. Of course, conversely, the first thin metal wires 12 a may bepatterned in the same manner as in the fourth conductive film 10D, andthe second thin metal wires 12 b may be patterned in the same manner asin the third conductive film 10C.

A conductive film according to a fifth embodiment (hereinafter referredto as the fifth conductive film 10E) will be described below withreference to FIG. 24.

As schematically shown in FIG. 24, the structure of the fifth conductivefilm 10E is approximately the same as that of the above first conductivefilm 10A, but different in the following respect.

Thus, the conductive portions 12 have a wavy line shape with a constantperiod. In the example of FIG. 24, 1 period of the arcs are arrangedbetween the intersections 24.

In the fifth conductive film 10E, the first line segment length La isequal to the second line segment length Lb, and the third line segmentlength Lc is equal to the fourth line segment length Ld, as in the firstconductive film 10A. However, as shown in FIG. 24, a pair of optionaltangent lines, which are positioned on the circumference line of eachmesh shape M symmetrically about the central point C of the mesh shapeM, are parallel to each other. Specifically, in FIG. 24, for example, apair of first tangent lines (1)(1), a pair of second tangent lines(2)(2), and a pair of third tangent lines (3)(3) are parallel to eachother, respectively, and have different tangent directions. In general,a light is highly refracted and diffracted in a tangent direction. Inthe fifth conductive film 10E, a light can be refracted and diffractedin a large number of the different tangent directions to reduce thesignificant glare.

Furthermore, in the fifth conductive film 10E, the opening portions 14have approximately constant opening areas, whereby the glare or the likecaused by the interference of diffracted lights can be prevented on thewhole surface, and the significant glare or the like is not causedlocally.

In addition, in the fifth conductive film 10E, the number of the arcs 26on the circumference line of one mesh shape M is 4k (k=1, 2, 3, . . . ).Therefore, the fifth conductive film 10E is capable of improving heatgeneration efficiency in a transparent heating element and improvingpower generation efficiency in a solar cell.

A conductive film according to a sixth embodiment (hereinafter referredto as the sixth conductive film 10F) will be described below withreference to FIG. 25.

As schematically shown in FIG. 25, the structure of the sixth conductivefilm 10F is approximately the same as that of the above fifth conductivefilm 10E.

Thus, in the sixth conductive film 10F, the first line segment length Lais equal to the second line segment length Lb as in the fifth conductivefilm 10E. In addition, a pair of optional tangent lines, which arepositioned on the circumference line of each mesh shape M symmetricallyabout the central point C of the mesh shape M, are parallel to eachother.

However, unlike the fifth conductive film 10E, in a line connecting thecentral points C3 and C4 of two optional mesh shapes M3 and M4adjacently disposed along the extending direction of the second thinmetal wire 12 b, the length Lc of a third line segment connecting thecentral point C3 of one mesh shape M3 and the first thin metal wire 12 ais different from the length Ld of a fourth line segment connecting thecentral point C4 of the other mesh shape M4 and the first thin metalwire 12 a. In the example of FIG. 25, the length Lc is larger than thelength Ld. It should be noted that the intersections 24 are at adistance of 0.5 periods in this example.

As in the fifth conductive film 10E, also in the sixth conductive film10F, a light can be refracted and diffracted in a large number of thedifferent tangent directions to reduce the significant glare.Furthermore, the opening portions 14 have approximately constant openingareas, whereby the glare or the like caused by the interference ofdiffracted lights can be prevented on the whole surface, and thesignificant glare or the like is not caused locally.

A conductive film according to a seventh embodiment (hereinafterreferred to as the seventh conductive film 10G) will be described belowwith reference to FIG. 26.

As schematically shown in FIG. 26, the structure of the seventhconductive film 10G is approximately the same as that of the above sixthconductive film 10F.

Thus, in the seventh conductive film 10G, the distance La is equal tothe distance Lb, the distance Lc is different from the distance Ld, anda pair of optional tangent lines, which are positioned on thecircumference line of each mesh shape M symmetrically about the centralpoint C of the mesh shape M, are parallel to each other.

The seventh conductive film 10G is different from the sixth conductivefilm 10F in that 1.5 periods of the arcs are arranged between theintersections 24.

Also in the seventh conductive film 10G, a light can be refracted anddiffracted in a large number of different directions to reduce thesignificant glare. Furthermore, the opening portions 14 haveapproximately constant opening areas, whereby the glare or the likecaused by the interference of diffracted lights can be prevented on thewhole surface, and the significant glare or the like is not causedlocally.

A conductive film according to an eighth embodiment (hereinafterreferred to as the eighth conductive film 10H) will be described belowwith reference to FIG. 27.

As schematically shown in FIG. 27, the structure of the eighthconductive film 10H is approximately the same as that of the above sixthconductive film 10F.

Thus, in the eighth conductive film 10H, the distance La is equal to thedistance Lb, the distance Lc is different from the distance Ld, and apair of optional tangent lines, which are positioned on thecircumference line of each mesh shape M symmetrically about the centralpoint C of the mesh shape M, are parallel to each other.

The eighth conductive film 10H is different from the sixth conductivefilm 10F in that the arc arrangement period between one intersection 24and a first intersection 24 a adjacently disposed at one side of the oneintersection 24 along the extending direction of the first thin metalwire 12 a is different from the arc arrangement period between the oneintersection 24 and a second intersection 24 b adjacently disposed atthe other side of the one intersection 24. In the example of FIG. 27, inthe arc arrangement, the one intersection 24 and the first intersection24 a are at a distance of 0.5 periods, and the one intersection 24 andthe second intersection 24 b are at a distance of 1.5 periods.

In addition, the arc arrangement period between the one intersection 24and a third intersection 24 c adjacently disposed at one side of the oneintersection 24 along the extending direction of the second thin metalwire 12 b is different from the arc arrangement period between the oneintersection 24 and a fourth intersection 24 d adjacently disposed atthe other side of the one intersection 24. In the example of FIG. 27, inthe arc arrangement, the one intersection 24 and the third intersection24 c are at a distance of 1.5 periods, and the one intersection 24 andthe fourth intersection 24 d are at a distance of 0.5 periods.

Also in the eighth conductive film 10H, a light can be refracted anddiffracted in a large number of different directions to reduce thesignificant glare.

In the fifth to eighth conductive films 10E to 10H as well as the firstconductive film 10A, the number of the arcs 26 on the circumference lineof one mesh shape M is 4k (k=1, 2, 3, . . . ). Therefore, the films arecapable of exhibiting a low overall surface resistance, improving heatgeneration efficiency in a transparent heating element, and improvingpower generation efficiency in a solar cell.

Then, several methods for producing the first to eighth conductive films10A to 10H (hereinafter collectively referred to as the conductive film10) will be described below with reference to FIGS. 28A to 31.

In the first production method, a photosensitive silver salt layer isformed, exposed, developed, and fixed on the transparent film substrate16 to form metallic silver portions. The metallic silver portions and aconductive metal disposed thereon are utilized for forming the meshpattern 22.

Specifically, as shown in FIG. 28A, the transparent film substrate 16 iscoated with a photosensitive silver salt layer 34 containing a mixtureof a gelatin 33 and a silver halide 31 (e.g., silver bromide particles,silver chlorobromide particles, or silver iodobromide particles). Thoughthe silver halide 31 is exaggeratingly shown by points in FIGS. 28A to28C to facilitate understanding, the points do not represent the size,concentration, etc.

Then, as shown in FIG. 28B, the photosensitive silver salt layer 34 issubjected to an exposure treatment for forming the mesh pattern 22. Whenan optical energy is applied to the silver halide 31, the silver halide31 is exposed to generate invisible minute silver nuclei, referred to asa latent image.

As shown in FIG. 28C, the photosensitive silver salt layer 34 issubjected to a development treatment for converting the latent image toan image visible to the naked eye. Specifically, the photosensitivesilver salt layer 34 having the latent image is developed using adeveloper, which is an alkaline or acidic solution, generally analkaline solution. In the development treatment, using the latent imagesilver nuclei as catalyst cores, silver ions from the silver halideparticles or the developer are reduced to metallic silver by a reducingagent in the developer (referred to as a developing agent). As a result,the latent image silver nuclei are grown to form a visible silver image(developed silver 35).

The photosensitive silver halide 31 remains in the photosensitive silversalt layer 34 after the development treatment. As shown in FIG. 28D, thesilver halide 31 is removed by a fixation treatment using a fixer, whichis an acidic or alkaline solution, generally an acidic solution.

After the fixation treatment, metallic silver portions 36 are formed inexposed areas, and light-transmitting portions 38 containing only thegelatin 33 are formed in unexposed areas. Thus, the combination of themetallic silver portions 36 and the light-transmitting portions 38 isformed on the transparent film substrate 16.

In a case where silver bromide is used as the silver halide 31 and athiosulfate salt is used in the fixation treatment, a reactionrepresented by the following formula proceeds in the treatment.AgBr (solid)+2 S₂O₃ ions→Ag(S₂O₃)₂ (readily-water-soluble complex)

Two thiosulfate S₂O₃ ions and one silver ion in the gelatin 33 (fromAgBr) are reacted to generate a silver thiosulfate complex. The silverthiosulfate complex has a high water solubility, and thereby is elutedfrom the gelatin 33. As a result, the developed silvers 35 are fixed andremain as the metallic silver portions 36.

Thus, the latent image is reacted with the reducing agent to deposit thedeveloped silvers 35 in the development treatment, and the residualsilver halide 31, not converted to the developed silvers 35, is elutedinto water in the fixation treatment. The treatments are described indetail in T. H. James, “The Theory of the Photographic Process, 4thed.”, Macmillian Publishing Co., Inc., NY, Chapter 15, pp. 438-442,1977.

The development treatment is generally carried out using the alkalinesolution. The alkaline solution used in the development treatment may bemixed into the fixer (generally an acidic solution), whereby theactivity of the fixer may be disadvantageously changed in the fixationtreatment. Further, the developer may remain on the film after removingthe film from the development bath, whereby an undesired developmentreaction may be accelerated by the developer. Thus, it is preferred thatthe photosensitive silver salt layer 34 is neutralized or acidified by aquencher such as an acetic acid solution after the development treatmentbefore the fixation treatment.

As shown in FIG. 28E, a conductive metal 40 may be disposed only on themetallic silver portions 36 by a plating treatment (such as anelectroless plating treatment, an electroplating treatment, or acombination thereof), etc. In this case, the mesh pattern 22 is formedof the metallic silver portions 36 on the transparent film substrate 16and the conductive metal 40 disposed on the metallic silver portions 36.

The difference between the above mentioned process using thephotosensitive silver salt layer 34 (a silver salt photographytechnology) and a process using a photoresist (a resist technology) willbe described below.

In the resist technology, a photopolymerization initiator absorbs alight in an exposure treatment to initiate a reaction, a photoresistfilm (a resin) per se undergoes a polymerization reaction to increase ordecrease the solubility in a developer, and the resin in an exposed orunexposed area is removed in a development treatment. The developerliquid used in the resist technology may be an alkaline solution free ofreducing agents, in which an unreacted resin component can be dissolved.On the other hand, as described above, in the silver salt photographytechnology according to the present invention, the minute silver nuclei(the so-called latent image) are formed from the silver ion and aphotoelectron generated in the silver halide 31 exposed in the exposuretreatment. The latent image silver nuclei are grown to form the visiblesilver image in the development treatment using the developer, whichmust contain the reducing agent (the developing agent). Thus, the resisttechnology and the silver salt photography technology are greatlydifferent in the reactions in the exposure and development treatments.

In the development treatment of the resist technology, the unpolymerizedresin portion in the exposed or unexposed area is removed. On the otherhand, in the development treatment of the silver salt photographytechnology, using the latent image as the catalyst core, the reductionreaction is conducted by the reducing agent contained in the developer(the developing agent), and the developed silver 35 is grown into avisible size. The gelatin 33 in the unexposed area is not removed. Thus,the resist technology and the silver salt photography technology aregreatly different also in the reactions in the development treatments.

The silver halide 31 contained in the gelatin 33 in the unexposed areais eluted in the following fixation treatment, and the gelatin 33 is notremoved.

The main reaction component (the main photosensitive component) is thesilver halide in the silver salt photography technology, while it is thephotopolymerization initiator in the resist technology. Further, in thedevelopment treatment, the binder (the gelatin 33) remains in the silversalt photography technology, while it is removed in the resisttechnology. The resist technology and the silver salt photographytechnology are greatly different in these points.

A mask used in the exposure treatment of the photosensitive silver saltlayer 34 may have a mask pattern corresponding to the mesh pattern 22 ofthe conductive portions 12 having the wavy line shape containing atleast one curve between the intersections 24.

In another method (the second production method), for example, as shownin FIG. 29A, a photoresist film 44 is formed on a copper foil 42disposed on the transparent film substrate 16, and the photoresist film44 is exposed and developed to form a resist pattern 46. As shown inFIG. 29B, the copper foil 42 exposed from the resist pattern 46 isetched to form the mesh pattern 22. In this method, a mask used in theexposure treatment of the photoresist film 44 may have a mask patterncorresponding to the mesh pattern 22.

In the third production method, as shown in FIG. 30A, a paste 48containing fine metal particles is printed on the transparent filmsubstrate 16. As shown in FIG. 30B, the printed paste 48 may be platedwith a metal 50 to form the mesh pattern 22.

In the fourth production method, as shown in FIG. 31, the mesh pattern22 may be printed on the transparent film substrate 16 by using a screenor gravure printing plate.

A particularly preferred method of forming a thin conductive metal filmusing a photographic photosensitive silver halide material for theconductive film 10 of this embodiment will be mainly described below.

As described above, the conductive film 10 of this embodiment may beproduced as follows. A photosensitive material having the transparentfilm substrate 16 and thereon a photosensitive silver halide-containingemulsion layer is exposed and developed, whereby the metallic silverportions 36 and the light-transmitting portions 38 are formed in theexposed areas and the unexposed areas respectively. The metallic silverportions 36 may be subjected to a physical development treatment and/ora plating treatment to deposit the conductive metal 40 thereon.

The method for forming the conductive film 10 of the embodiment includesthe following three processes, depending on the photosensitive materialsand development treatments.

(1) A process comprising subjecting a photosensitive black-and-whitesilver halide material free of physical development nuclei to a chemicalor thermal development, to form the metallic silver portions 36 on thephotosensitive material.

(2) A process comprising subjecting a photosensitive black-and-whitesilver halide material having a silver halide emulsion layer containingphysical development nuclei to a solution physical development, to formthe metallic silver portions 36 on the photosensitive material.

(3) A process comprising subjecting a stack of a photosensitiveblack-and-white silver halide material free of physical developmentnuclei and an image-receiving sheet having a non-photosensitive layercontaining physical development nuclei to a diffusion transferdevelopment, to form the metallic silver portions 36 on thenon-photosensitive image-receiving sheet.

In the process of (1), an integral black-and-white development procedureis used to form a transmittable conductive film such as anelectromagnetic-shielding film or a light-transmitting conductive filmon the photosensitive material. The resulting silver is a chemically orthermally developed silver containing a high-specific surface areafilament, and thereby shows a high activity in the following plating orphysical development treatment.

In the process of (2), the silver halide particles are melted around thephysical development nuclei and deposited on the nuclei in the exposedareas, to form a transmittable conductive film such as alight-transmitting electromagnetic-shielding film or alight-transmitting conductive film on the photosensitive material. Alsoin this process, an integral black-and-white development procedure isused. Though high activity can be achieved since the silver halide isdeposited on the physical development nuclei in the development, thedeveloped silver has a spherical shape with small specific surface.

In the process of (3), the silver halide particles are melted inunexposed areas, and diffused and deposited on the development nuclei ofthe image-receiving sheet, to form a transmittable conductive film suchas an electromagnetic-shielding film or a light-transmitting conductivefilm on the sheet. In this process, a so-called separate-type procedureis used, and the image-receiving sheet is peeled off from thephotosensitive material.

A negative or reversal development treatment can be used in theprocesses. In the diffusion transfer development, the negativedevelopment treatment can be carried out using an auto-positivephotosensitive material.

The chemical development, thermal development, solution physicaldevelopment, and diffusion transfer development have the meaningsgenerally known in the art, and are explained in common photographicchemistry texts such as Shin-ichi Kikuchi, “Shashin Kagaku (PhotographicChemistry)”, Kyoritsu Shuppan Co., Ltd., 1955 and C. E. K. Mees, “TheTheory of Photographic Processes, 4th ed.”, Mcmillan, 1977. A liquidtreatment is generally used in the present invention, and also a thermaldevelopment treatment can be utilized. For example, techniques describedin Japanese Laid-Open Patent Publication Nos. 2004-184693, 2004-334077,and 2005-010752, and Japanese Patent Application Nos. 2004-244080 and2004-085655 can be used in the present invention.

(Photosensitive Material)

[Transparent Support]

The transparent film substrate 16 of the photosensitive material used inthe production method of the embodiment may be a plastic film, etc.

In this embodiment, it is preferred that the plastic film is apolyethylene terephthalate film or a triacetyl cellulose (TAC) film fromthe viewpoints of light transmittance, heat resistance, handling, andcost.

In a transparent heating element for a window glass, the transparentfilm substrate 16 preferably has a high light transmittance. In thiscase, the total visible light transmittance of the plastic film ispreferably 70% to 100%, more preferably 85% to 100%, particularlypreferably 90% to 100%. The plastic film may be colored as long as itdoes not interfere with the advantageous effects of the presentinvention.

[Protective Layer]

In the photosensitive material, a protective layer may be formed on theemulsion layer to be hereinafter described. The protective layer used inthis embodiment contains a binder such as a gelatin or a high-molecularpolymer, and is formed on the photosensitive emulsion layer to improvethe scratch prevention or mechanical property.

[Emulsion Layer]

The photosensitive material used in the production method of thisembodiment preferably has the transparent film substrate 16 and thereonthe emulsion layer containing the silver salt as a light sensor (thesilver salt-containing layer). The emulsion layer according to theembodiment may contain a dye, a binder, a solvent, etc. in addition tothe silver salt if necessary.

The ratio of the dye to the total solid contents in the emulsion layeris preferably 0.01% to 10% by mass, more preferably 0.1% to 5% by mass,in view of the effects such as the irradiation prevention effect and thesensitivity reduction due to the excess addition.

<Silver Salt>

The silver salt used in this embodiment is preferably an inorganicsilver salt such as a silver halide. It is particularly preferred thatthe silver salt is used in the form of particles for the photographicphotosensitive silver halide material. The silver halide has anexcellent light sensing property.

The silver halide, preferably used in the photographic emulsion of thephotographic photosensitive silver halide material, will be describedbelow.

In this embodiment, the silver halide is preferably used as a lightsensor. Silver halide technologies for photographic silver salt films,photographic papers, print engraving films, emulsion masks forphotomasking, and the like may be utilized in this embodiment.

The silver halide may contain a halogen element of chlorine, bromine,iodine, or fluorine, and may contain a combination of the elements. Forexample, the silver halide preferably contains AgCl, AgBr, or AgI, morepreferably contains AgBr or AgCl, as a main component. Also silverchlorobromide, silver iodochlorobromide, or silver iodobromide ispreferably used as the silver halide. The silver halide is furtherpreferably silver chlorobromide, silver bromide, silveriodochlorobromide, or silver iodobromide, most preferably silverchlorobromide or silver iodochlorobromide having a silver chloridecontent of 50 mol % or more.

The term “the silver halide contains AgBr (silver bromide) as a maincomponent” means that the mole ratio of bromide ion is 50% or more inthe silver halide composition. The silver halide particle containingAgBr as a main component may contain iodide or chloride ion in additionto the bromide ion.

The silver halide emulsion, used as a coating liquid for the emulsionlayer in this embodiment, may be prepared by a method described in P.Glafkides, “Chimie et Physique Photographique”, Paul Montel, 1967, G. F.Dufin, “Photographic Emulsion Chemistry”, The Forcal Press, 1966, V. L.Zelikman, et al., “Making and Coating Photographic Emulsion”, The ForcalPress, 1964, etc.

<Binder>

The binder may be used in the emulsion layer to uniformly disperse thesilver salt particles and to help the emulsion layer adhere to asupport. In the present invention, the binder may contain awater-insoluble or water-soluble polymer, and preferably contains awater-soluble polymer.

Examples of the binders include gelatins, polyvinyl alcohols (PVA),polyvinyl pyrolidones (PVP), polysaccharides such as starches,celluloses and derivatives thereof, polyethylene oxides,polysaccharides, polyvinylamines, chitosans, polylysines, polyacrylicacids, polyalginic acids, polyhyaluronic acids, and carboxycelluloses.The binders show a neutral, anionic, or cationic property depending onthe ionicity of a functional group.

<Solvent>

The solvent used for forming the emulsion layer is not particularlylimited, and examples thereof include water, organic solvents (e.g.alcohols such as methanol, ketones such as acetone, amides such asformamide, sulfoxides such as dimethyl sulfoxide, esters such as ethylacetate, ethers), ionic liquids, and mixtures thereof.

In the present invention, the ratio of the solvent to the total of thesilver salt, the binder, and the like in the emulsion layer is 30% to90% by mass, preferably 50% to 80% by mass.

The treatments for forming the conductive film will be described below.

[Exposure]

In this embodiment, though the mesh pattern 22 may be formed by aprinting process, it is formed by the exposure and developmenttreatments, etc. in another process. A photosensitive material havingthe transparent film substrate 16 and thereon the silver salt-containinglayer formed thereon or a photosensitive material coated with aphotopolymer for photolithography is subjected to the exposuretreatment. An electromagnetic wave may be used in the exposure. Forexample, the electromagnetic wave may be a light such as a visible lightor an ultraviolet light, or a radiation ray such as an X-ray. Theexposure may be carried out using a light source having a wavelengthdistribution or a specific wavelength.

[Development Treatment]

In this embodiment, the emulsion layer is subjected to the developmenttreatment after the exposure. Common development treatment technologiesfor photographic silver salt films, photographic papers, print engravingfilms, emulsion masks for photomasking, and the like may be used in thepresent invention. A developer for the development treatment is notparticularly limited, and may be a PQ developer, an MQ developer, an MAAdeveloper, etc. Examples of commercially available developers usable inthe present invention include CN-16, CR-56, CP45X, FD-3, and PAPITOLavailable from FUJIFILM Corporation, C-41, E-6, RA-4, D-19, and D-72available from Eastman Kodak Company, and developers contained in kitsthereof. The developer may be a lith developer.

In the present invention, the development process may include a fixationtreatment for removing the silver salt in the unexposed area tostabilize the material. Fixation treatment technologies for photographicsilver salt films, photographic papers, print engraving films, emulsionmasks for photomasking, and the like may be used in the presentinvention.

In the fixation treatment, the fixation temperature is preferably about20° C. to 50° C., more preferably 25° C. to 45° C. The fixation time ispreferably 5 seconds to 1 minute, more preferably 7 to 50 seconds. Theamount of the fixer is preferably 600 ml/m² or less, more preferably 500ml/m² or less, particularly preferably 300 ml/m² or less, per 1 m² ofthe photosensitive material to be treated.

The developed and fixed photosensitive material is preferably subjectedto a water washing treatment or a stabilization treatment. The amount ofwater used in the water washing or stabilization treatment is generally20 L or less, and may be 3 L or less, per 1 m² of the photosensitivematerial. The photosensitive material may be washed with storage water,and thus the water amount may be 0.

The ratio of the metallic silver contained in the exposed area after thedevelopment to the silver contained in this area before the exposure ispreferably 50% or more, more preferably 80% or more by mass. When theratio is 50% or more by mass, a high conductivity can be achieved.

In this embodiment, the tone (gradation) obtained by the development ispreferably more than 4.0, though not particularly restrictive. When thetone is more than 4.0 after the development, the conductivity of theconductive metal portion can be increased while maintaining hightransmittance of the light-transmitting portion. For example, the toneof 4.0 or more can be achieved by doping with rhodium or iridium ion.

[Physical Development and Plating Treatment]

In this embodiment, to increase the conductivity of the metallic silverportion formed by the above exposure and development treatments,conductive metal particles may be deposited thereon by a physicaldevelopment treatment and/or a plating treatment. In the presentinvention, the conductive metal particles may be deposited on themetallic silver portion by only one of the physical development andplating treatments or by the combination of the treatments. The metallicsilver portion, subjected to the physical development treatment and/orthe plating treatment in this manner, is referred to as the conductivemetal portion.

In this embodiment, the physical development is such a process thatmetal ions such as silver ions are reduced by a reducing agent, wherebymetal particles are deposited on a metal or metal compound core. Suchphysical development has been used in the fields of instant B & W film,instant slide film, printing plate production, etc., and thetechnologies can be used in the present invention.

The physical development may be carried out at the same time as theabove development treatment after the exposure, and may be carried outafter the development treatment separately.

In this embodiment, the plating treatment may contain electrolessplating (such as chemical reduction plating or displacement plating),electrolytic plating, or a combination thereof. Known electrolessplating technologies for printed circuit boards, etc. may be used inthis embodiment. The electroless plating is preferably electrolesscopper plating.

[Oxidation Treatment]

In this embodiment, the metallic silver portion formed by thedevelopment treatment or the conductive metal portion formed by thephysical development treatment and/or the plating treatment ispreferably subjected to an oxidation treatment. For example, by theoxidation treatment, a small amount of a metal deposited on thelight-transmitting portion can be removed, so that the transmittance ofthe light-transmitting portion can be increased to approximately 100%.

[Conductive Metal Portion]

In this embodiment, the line width of the conductive metal portion maybe selected within a range of 5 m to 200 μm (0.2 mm). In the case ofusing the conductive metal portion for a transparent heating element,the portion may have a part with a line width of more than 20 μm for thepurpose of ground connection, etc.

The line width is preferably 5 to 50 μm, more preferably 5 to 30 μm,most preferably 10 to 25 μm. The line distance is preferably 50 to 500μm, more preferably 200 to 400 μm, most preferably 250 to 350 μm.

In this embodiment, the opening ratio of the conductive metal portion ispreferably 85% or more, more preferably 90% or more, most preferably 95%or more, in view of the visible light transmittance. The opening ratiois the ratio of the light-transmitting portions other than the metalportions in the mesh pattern 22 to the whole. For example, a squarelattice mesh having a line width of 15 μm and a pitch of 300 μm has anopening ratio of 90%.

[Light-Transmitting Portion]

In this embodiment, the light-transmitting portion is a portion havinglight transmittance, other than the conductive metal portions in theconductive film 10. The transmittance of the light-transmitting portion,which is herein a minimum transmittance value in a wavelength region of380 to 780 nm obtained neglecting the light absorption and reflection ofthe transparent film substrate 16, is 90% or more, preferably 95% ormore, more preferably 97% or more, further preferably 98% or more, mostpreferably 99% or more.

In this embodiment, it is preferred that the mesh pattern 22 has acontinuous structure with a length of 3 m or more from the viewpoint ofmaintaining a high productivity of the conductive film 10. As the lengthof the continuous structure of the mesh pattern 22 is increased, thiseffect is further improved. Thus, in this case, the production loss of atransparent heating element can be advantageously reduced. The long rollof the mesh pattern 22, which contains the conductive portions 12 formedin the wavy line shape having at least one curve between theintersections 24, may be printing-exposed by a surface exposure methodof irradiating the roll with a uniform light through a patterned mask ora scanning exposure method of irradiating the roll with a laser beamwhile transporting.

When an excessively large number of grids of the mesh pattern 22 (themesh shapes M) are continuously printed, the roll of the mesh pattern 22is disadvantageous in large diameter, heavy weight, and that highpressure is applied to the roll center to cause adhesion or deformation,etc. Therefore, the length of the mesh pattern 22 is preferably 2000 mor less. The length is preferably 3 m or more, more preferably 100 to1000 m, further preferably 200 to 800 m, most preferably 300 to 500 m.

The thickness of the transparent film substrate 16 may be selected forexample within a range of 0.01 to 2.0 mm. In view of the above describedweight increase, adhesion, deformation, etc. caused in the roll, thethickness of the transparent film substrate 16 is preferably 200 μm orless, more preferably 20 to 180 μm, most preferably 50 to 120 μm.

In this embodiment, for example, in the first conductive film 10A shownin FIG. 1, it is preferred that an imaginary line connecting theintersections 24 of the first thin metal wire 12 a is parallel to theadjacent imaginary line within an error of plus or minus 2°.

The scanning exposure with the optical beam is preferably carried outusing light sources arranged on a line in a direction substantiallyperpendicular to the transporting direction, or using a rotary polygonmirror. In this case, the optical beam has to undergo binary or moreintensity modulation, and dots are continuously formed into a linepattern. Because each fine wire is composed of the continuous dots, afine 1-dot wire has a steplike edge shape. The width of each fine wireis a length in the narrowest part.

In this embodiment, the mesh pattern 22 is tilted preferably at 30° to60°, more preferably at 40° to 50°, most preferably at 43° to 47°,against the transporting direction. In general, it is difficult toprepare a mask for forming a mesh pattern tilted at about 45° againstthe frame, and this is likely to result in uneven pattern, increasedcost, etc. In contrast, in the above method according to the presentinvention, the pattern unevenness is reduced at the tilt angle of around45°. Thus, the method of the embodiment is more effective as comparedwith patterning methods using masking exposure photolithography orscreen printing.

[Conductive Film]

In the conductive film 10 of this embodiment, the thickness of thetransparent film substrate 16 may be selected within a range of 0.01 to2.0 mm as described above. The thickness is preferably 5 to 200 μm, morepreferably 30 to 150 μm. When the thickness is 5 to 200 μm, a desiredvisible light transmittance can be obtained, and the transparent filmsubstrate 16 can be easily handled.

The thickness of the metallic silver portion 36 formed on the supportbefore the physical development treatment and/or the plating treatmentmay be appropriately selected by controlling the thickness of thecoating liquid for the silver salt-containing layer applied to thetransparent film substrate 16. The thickness of the metallic silverportion 36 may be selected within a range of 0.001 to 0.2 mm, and ispreferably 30 μm or less, more preferably 20 μm or less, furtherpreferably 0.01 to 9 μm, most preferably 0.05 to 5 μm. The metallicsilver portion 36 is preferably formed in a patterned shape. Themetallic silver portion 36 may have a monolayer structure or amultilayer structure containing two or more layers. In a case where themetallic silver portion 36 has a patterned multilayer structurecontaining two or more layers, the layers may have different wavelengthcolor sensitivities. In this case, different patterns can be formed inthe layers by using exposure lights with different wavelengths.

In the case of using the conductive film 10 in a transparent heatingelement, the conductive metal portion preferably has a smallerthickness. As the thickness is reduced, the viewing angle of a windowglass using the element is increased, and the heat generation efficiencyis improved. Thus, the thickness of the layer of the conductive metal 40on the conductive metal portion is preferably less than 9 μm, morepreferably 0.1 μm or more but less than 5 μm, further preferably 0.1 μmor more but less than 3 μm.

In this embodiment, the thickness of the metallic silver portion 36 canbe controlled by changing the coating thickness of the silversalt-containing layer, and the thickness of the conductive metalparticle layer can be controlled in the physical development and/or theplating treatment, whereby the conductive film 10 having a thickness ofless than 5 μm (preferably less than 3 μm) can be easily produced.

In conventional etching methods, most of a thin metal film must beremoved and discarded by etching. In contrast, in this embodiment, thepattern containing only a minimal amount of the conductive metal can beformed on the transparent film substrate 16. Thus, only the minimalamount of the metal is required, so that production costs and metalwaste amount can be advantageously reduced.

<Adhesive Layer>

The conductive film 10 of the embodiment may be bonded to a windowglass, etc. by an adhesive layer. The adhesive layer preferably containsan adhesive having a refractive index of 1.40 to 1.70. This is becausevisible light transmittance deterioration can be prevented by reducingthe refractive index difference between the adhesive and the transparentsubstrate such as the plastic film. When the adhesive has a refractiveindex of 1.40 to 1.70, the visible light transmittance deterioration canbe advantageously reduced.

EXAMPLES

The present invention will be described more specifically below withreference to Examples 1 and 2. Materials, amounts, ratios, treatmentcontents, treatment procedures, and the like, used in Examples 1 and 2,may be appropriately changed without departing from the scope of thepresent invention. The following specific examples are therefore to beconsidered in all respects as illustrative and not restrictive.

(Photosensitive Silver Halide Material: Examples 1 and 2)

An emulsion containing an aqueous medium, a gelatin, and silveriodobromochloride particles was prepared. The amount of the gelatin was10.0 g per 60 g of Ag, and the silver iodobromochloride particles had anI content of 0.2 moil, a Br content of 40 moil, and an average sphericalequivalent diameter of 0.1 μm.

K3Rh2Br9 and K2IrCl6 were added to the emulsion at a concentration of10⁻⁷ mol/mol-silver to dope the silver bromide particles with Rh and Irions. Na2PdCl4 was further added to the emulsion, and the resultantemulsion was subjected to gold-sulfur sensitization using chlorauricacid and sodium thiosulfate. The emulsion and a gelatin hardening agentwere applied to a polyethylene terephthalate (PET) such that the amountof the applied silver was 1 g/m². The Ag/gelatin volume ratio was 1/2.

The PET support had a width of 30 cm, and the emulsion was appliedthereto into a width of 25 cm and a length of 20 m. The both endportions having a width of 3 cm of the PET support were cut off toobtain a roll photosensitive silver halide material having a width of 24cm.

(Exposure)

The photosensitive silver halide material was exposed by using acontinuous exposure apparatus. In the apparatus, exposure heads using aDMD (a digital mirror device) according to an embodiment of JapaneseLaid-Open Patent Publication No. 2004-1244 were arranged into a width of25 cm. The exposure heads and exposure stages were arranged on a curvedline to concentrate laser lights onto the photosensitive layer of thephotosensitive material. Further, in the apparatus, a feeding mechanismand a winding mechanism for the photosensitive material were disposed,and a buffering bend was formed such that the speed in the exposure partwas not affected by change of the exposure surface tension, and feedingand winding speeds. The light for the exposure had a wavelength of 400nm and a beam shape of approximately 12-μm square, and the output of thelaser light source was 100 μJ.

The photosensitive material was exposed continuously in a pattern shownin Table 1 with a width of 24 cm and a length of 10 m. The exposure wascarried out under the following conditions to print a mesh pattern 22.The periods of wavy line shapes between intersections 24 in the meshpattern 22, the first pitch L1 (the pitch of first thin metal wires 12a), the second pitch L2 (the pitch of second thin metal wires 12 b) areshown in Table 1.

The mesh pattern 22 was formed on the photosensitive layer by anexposure method using two exposure heads in combination.

By using the first exposure head, the photosensitive layer is irradiatedwith a constant laser beam while reciprocating the beam in the directionperpendicular to the direction of transporting the layer, to draw anexposure pattern (for forming the first thin metal wires 12 a) on thelayer. Thus, the pattern is drawn by the beam at a tilt angle of 45° inaccordance with the ratio of the photosensitive layer transporting speedand the head reciprocating speed in the perpendicular direction. Afterthe beam reaches an end of the photosensitive layer, the pattern isdrawn at the reversed angle depending on the reciprocal motion of thehead.

Specifically, in Example 1, an exposure pattern for forming the firstthin metal wires 12 a shown in FIG. 1 was drawn. In Example 2, anexposure pattern for forming the first thin metal wires 12 a shown inFIG. 4 was drawn.

By using the second exposure head, in the same manner as in the firstexposure head, the photosensitive layer is irradiated with a constantlaser beam while reciprocating the beam in the direction perpendicularto the direction of transporting the layer, to draw an exposure pattern(for forming the second thin metal wires 12 b) on the layer. The motionstart point of the second exposure head is different from that of thefirst exposure head by 180 degrees or a multiple of 180 degrees. Thus,when the first exposure head is moved obliquely from one end of thephotosensitive layer, the second exposure head is moved obliquely fromthe other end in the opposite direction, so that the mesh pattern 22 isformed.

Specifically, in Example 1, an exposure pattern for forming the secondthin metal wires 12 b shown in FIG. 1 was drawn. In Example 2, anexposure pattern for forming the second thin metal wires 12 b shown inFIG. 4 was drawn.

(Development treatment) Formulation of 1 L of developer Hydroquinone 20g Sodium sulfite 50 g Potassium carbonate 40 gEthylenediaminetetraacetic acid 2 g Potassium bromide 3 g Polyethyleneglycol 2000 1 g Potassium hydroxide 4 g pH Controlled at 10.3Formulation of 1 L of fixer Ammonium thiosulfate solution (75%) 300 mlAmmonium sulfite monohydrate 25 g 1,3-Diaminopropanetetraacetic acid 8 gAcetic acid 5 g Aqueous ammonia (27%) 1 g pH Controlled at 6.2

The exposed photosensitive material was treated with the above treatmentagents under the following conditions using an automatic processorFG-710PTS manufactured by FUJIFILM Corporation. A development treatmentwas carried out at 35° C. for 30 seconds, a fixation treatment wascarried out at 34° C. for 23 seconds, and then a water washing treatmentwas carried out for 20 seconds at a water flow rate of 5 L/min.

The running conditions were such that the amount of the treatedphotosensitive material was 100 m²/day, the replenishment amount of thedeveloper was 500 ml/m², the replenishment amount of the fixer was 640ml/m², and the treatment period was 3 days. It was confirmed that acopper pattern had a line width of 12 μm and a pitch of 300 μm after aplating treatment.

The material was subjected to an electroless copper plating treatment at45° C. using an electroless Cu plating solution having a pH of 12.5,containing 0.06 mol/L of copper sulfate, 0.22 mol/L of formalin, 0.12mol/L of triethanolamine, 100 ppm of a polyethylene glycol, 50 ppm ofyellow prussiate of potash, and 20 ppm of α,α′-bipyridine. The materialwas then subjected to an oxidation treatment using an aqueous solutioncontaining 10 ppm of Fe (III) ion, to produce each conductive filmsample.

As shown in Table 1, in Example 1 (see FIG. 1), one first thin metalwires 12 a 1 and one second thin metal wires 12 b 1 had 1 period of thewavy line shape between the intersections 24, the other first thin metalwires 12 a 2 and the other second thin metal wires 12 b 2 had 2 periodsof the wavy line shape between the intersections 24, the first pitch L1and the second pitch L2 were 400 μm, and the line width h of theconductive portions 12 was 18 μm. In Example 2 (see FIG. 4), one firstthin metal wires 12 a 1 and one second thin metal wires 12 b 1 had 1period of the wavy line shape between the intersections 24, the firstpitch L1 and the second pitch L2 were 400 μm, and the line width h ofthe conductive portions 12 was 18 μm.

[Evaluation]

(Surface Resistance Measurement)

In each conductive film 10, the surface resistivity values of optionallyselected 10 areas were measured by LORESTA GP (Model No. MCP-T610)manufactured by Dia Instruments Co., Ltd. utilizing an in-linefour-probe method (ASP), and the average of the measured values wasobtained to evaluate the surface resistivity uniformity.

(Glare Evaluation)

A transparent plate for supporting each conductive film 10 was composedof a glass with a thickness of 5 mm representing a window glass. Theconductive film was attached to the transparent plate and placed in adark room. A light was emitted from an incandescent lamp (40-watt bulb)placed at a distance of 3 m from the transparent plate. The lighttransmitted through the transparent plate was visually observed toevaluate the glare caused by interference of a diffracted light. Theglare observation was carried out in a position at a distance of 1 mfrom the surface of the transparent plate (the surface on which theconductive film 10 was attached). When the glare was not observed, thesample was evaluated as Excellent. When the glare was slightly observedbut acceptable, the sample was evaluated as Fair. When the glare wassignificantly observed, the sample was evaluated as Poor.

(Evaluation Result)

As shown in Table 1, in Examples 1 and 2, each sample had no significantglare, a low surface resistivity sufficient for practical use in atransparent heating element, and an excellent light transmittance. Inaddition, conductive films were produced in the same manner as inExample 1 except for using mesh patterns shown in FIGS. 14 and 23,respectively. Also, each of the conductive films had no significantglare, a low surface resistivity sufficient for practical use in atransparent heating element, and an excellent light transmittance.

TABLE 1 Period First Second Total between pitch pitch Surface lightinter- L1 L2 resistivity transmit- sections (μm) (μm) Glare (ohm/sq)tance (%) Example 1 1 and 2 400 400 Excellent 0.3 80.1 Example 2 1 and400 400 Excellent 0.3 81.2 straight

It is to be understood that the conductive film and the transparentheating element of the present invention are not limited to the aboveembodiments, and various changes and modifications may be made thereinwithout departing from the scope of the present invention.

The present invention may be appropriately combined with technologiesdescribed in the following patent publications: Japanese Laid-OpenPatent Publication Nos. 2004-221564, 2004-221565, 2007-200922, and2006-352073; International Patent Publication No. 2006/001461; JapaneseLaid-Open Patent Publication Nos. 2007-129205, 2007-235115, 2007-207987,2006-012935, 2006-010795, 2006-228469, 2006-332459, 2007-207987, and2007-226215; International Patent Publication No. 2006/088059; JapaneseLaid-Open Patent Publication Nos. 2006-261315, 2007-072171, 2007-102200,2006-228473, 2006-269795, and 2006-267635; International PatentPublication No. 2006/098333; Japanese Laid-Open Patent Publication Nos.2006-324203, 2006-228478, and 2006-228836; International PatentPublication Nos. 2006/098336 and 2006/098338; Japanese Laid-Open PatentPublication Nos. 2007-009326, 2006-336090, 2006-336099, 2006-348351,2007-270321, and 2007-270322; International Patent Publication No.2006/098335; Japanese Laid-Open Patent Publication Nos. 2007-201378 and2007-335729; International Patent Publication No. 2006/098334; JapaneseLaid-Open Patent Publication Nos. 2007-134439, 2007-149760, 2007-208133,2007-178915, 2007-334325, 2007-310091, 2007-116137, 2007-088219,2007-207883, and 2007-013130; International Patent Publication No.2007/001008; and Japanese Laid-Open Patent Publication Nos. 2005-302508,2008-218784, 2008-227350, 2008-227351, 2008-244067, 2008-267814,2008-270405, 2008-277675, 2008-277676, 2008-282840, 2008-283029,2008-288305, 2008-288419, 2008-300720, 2008-300721, 2009-4213,2009-10001, 2009-16526, 2009-21334, 2009-26933, 2008-147507,2008-159770, 2008-159771, 2008-171568, 2008-198388, 2008-218096,2008-218264, 2008-224916, 2008-235224, 2008-235467, 2008-241987,2008-251274, 2008-251275, 2008-252046, 2008-277428, and 2009-21153.

The invention claimed is:
 1. A conductive film comprising a plurality ofconductive portions and a plurality of opening portions, wherein acombination of the conductive portions and the opening portions has meshshapes, the conductive portions are formed of a plurality of conductivethin metal wires in a mesh pattern having a plurality of latticeintersections, the mesh pattern is formed by crossing a plurality offirst thin metal wires arranged in one direction and a plurality ofsecond thin metal wires arranged in another direction, and some of thefirst thin metal wires are formed in wavy line shapes containing arcsextending in alternate directions, at least one of the arcs beingdisposed between the intersections, and the wavy line shapes of adjacentparallel first thin metal wires have different periods, wherein in animaginary line connecting central points of adjacent two mesh shapeswhich share only a single intersection of the conductive portions, alength between the central point of one of the two adjacent mesh shapesand the shared intersection is equal to a length between the centralpoint of another of the two adjacent mesh shapes and the sharedintersection.
 2. The conductive film according to claim 1, wherein thearcs have a central angle of 75° to 105°.
 3. The conductive filmaccording to claim 1, wherein the second thin metal wires are formed inwavy line shapes containing at least one curve between theintersections, and the wavy line shapes of adjacent parallel second thinmetal wires have different periods.
 4. The conductive film according toclaim 1, wherein at least one of a pattern of the first thin metal wiresand a pattern of the second thin metal wires is arranged such that onethin metal wire has a smallest arrangement period number of the arcs,and the arrangement period number of the arcs is increased stepwise fromthe one thin metal wire to another thin metal wire arranged in onedirection.
 5. The conductive film according to claim 1, wherein at leastone of a pattern of the first thin metal wires and a pattern of thesecond thin metal wires is arranged such that two thin metal wiresdisposed adjacently on either side of a thin metal wire having asmallest arrangement period number of the arcs have approximately thesame arrangement period numbers of the arcs, and two thin metal wiresdisposed adjacently on either side of a thin metal wire having a largestarrangement period number of the arcs have approximately the samearrangement period numbers of the arcs.
 6. The conductive film accordingto claim 1, wherein the conductive portions have a crossing angle ofapproximately 90° in the intersections.
 7. The conductive film accordingto claim 1, wherein the conductive portions contain a metallic silverportion formed by exposing and developing a photosensitive silver saltlayer disposed on a transparent support.
 8. A conductive film comprisinga plurality of conductive portions and a plurality of opening portions,wherein a combination of the conductive portions and the openingportions has mesh shapes, the conductive portions are formed of aplurality of conductive thin metal wires in a mesh pattern having aplurality of lattice intersections, the mesh pattern is formed bycrossing a plurality of first thin metal wires arranged in one directionand a plurality of second thin metal wires arranged in anotherdirection, some of the first thin metal wires are formed in a wavy lineshape containing arcs extending in alternate directions, at least one ofthe arcs being disposed between the intersections, and among adjacentparallel first thin metal wires, one first thin metal wire is formed ina straight line shape, wherein in an imaginary line connecting centralpoints of adjacent two mesh shapes which share only a singleintersection of the conductive portions, a length between the centralpoint of one of the two adjacent mesh shapes and the shared intersectionis equal to a length between the central point of another of the twoadjacent mesh shapes and the shared intersection.
 9. The conductive filmaccording to claim 8, wherein the arcs have a central angle of 75° to105°.
 10. The conductive film according to claim 8, wherein amongadjacent parallel second thin metal wires, one second thin metal wire isformed in a straight line shape, and the other second thin metal wire isformed in a wavy line shape containing at least one curve between theintersections.
 11. The conductive film according to claim 8, wherein atleast one of a pattern of the first thin metal wires and a pattern ofthe second thin metal wires is arranged such that one thin metal wirehas a smallest arrangement period number of the arcs, and thearrangement period number of the arcs is increased stepwise from the onethin metal wire to another thin metal wire arranged in one direction.12. The conductive film according to claim 8, wherein at least one of apattern of the first thin metal wires and a pattern of the second thinmetal wires is arranged such that two thin metal wires disposedadjacently on either side of a thin metal wire having a smallestarrangement period number of the arcs have approximately the samearrangement period numbers of the arcs, and two thin metal wiresdisposed adjacently on either side of a thin metal wire having a largestarrangement period number of the arcs have approximately the samearrangement period numbers of the arcs.
 13. The conductive filmaccording to claim 8, wherein the conductive portions have a crossingangle of approximately 90° in the intersections.
 14. The conductive filmaccording to claim 8, wherein the conductive portions contain a metallicsilver portion formed by exposing and developing a photosensitive silversalt layer disposed on a transparent support.
 15. A conductive filmcomprising a plurality of conductive portions and a plurality of openingportions, wherein a combination of the conductive portions and theopening portions has mesh shapes, the conductive portions are formed ofa plurality of conductive thin metal wires in a mesh pattern having aplurality of lattice intersections, the mesh pattern is formed bycrossing a plurality of first thin metal wires arranged in one directionand a plurality of second thin metal wires arranged in anotherdirection, and some of the first thin metal wires are formed in wavyline shapes containing arcs extending in alternate directions, at leastone of the arcs being disposed between the intersections, and the wavyline shapes of adjacent parallel first thin metal wires have differentperiods, wherein a length of a straight imaginary line connectingcentral points of adjacent two mesh shapes, which share one side of themesh shapes, is equally divided by a shared side.
 16. The conductivefilm according to claim 15, wherein the arcs have a central angle of 75°to 105°.
 17. The conductive film according to claim 15, wherein thesecond thin metal wires are formed in wavy line shapes containing atleast one curve between the intersections, and the wavy line shapes ofadjacent parallel second thin metal wires have different periods. 18.The conductive film according to claim 15, wherein at least one of apattern of the first thin metal wires and a pattern of the second thinmetal wires is arranged such that one thin metal wire has a smallestarrangement period number of the arcs, and the arrangement period numberof the arcs is increased stepwise from the one thin metal wire toanother thin metal wire arranged in one direction.
 19. The conductivefilm according to claim 15, wherein at least one of a pattern of thefirst thin metal wires and a pattern of the second thin metal wires isarranged such that two thin metal wires disposed adjacently on eitherside of a thin metal wire having a smallest arrangement period number ofthe arcs have approximately the same arrangement period numbers of thearcs, and two thin metal wires disposed adjacently on either side of athin metal wire having a largest arrangement period number of the arcshave approximately the same arrangement period numbers of the arcs. 20.The conductive film according to claim 15, wherein the conductiveportions have a crossing angle of approximately 90° in theintersections.
 21. The conductive film according to claim 15, whereinthe conductive portions contain a metallic silver portion formed byexposing and developing a photosensitive silver salt layer disposed on atransparent support.
 22. A conductive film comprising a plurality ofconductive portions and a plurality of opening portions, wherein acombination of the conductive portions and the opening portions has meshshapes, the conductive portions are formed of a plurality of conductivethin metal wires in a mesh pattern having a plurality of latticeintersections, the mesh pattern is formed by crossing a plurality offirst thin metal wires arranged in one direction and a plurality ofsecond thin metal wires arranged in another direction, some of the firstthin metal wires are formed in a wavy line shape containing arcsextending in alternate directions, at least one of the arcs beingdisposed between the intersections, and among adjacent parallel firstthin metal wires, one first thin metal wire is formed in a straight lineshape, wherein a length of a straight imaginary line connecting centralpoints of adjacent two mesh shapes, which share one side of the meshshapes, is equally divided by the shared side.
 23. The conductive filmaccording to claim 22, wherein the arcs have a central angle of 75° to105°.
 24. The conductive film according to claim 22, wherein amongadjacent parallel second thin metal wires, one second thin metal wire isformed in a straight line shape, and the other second thin metal wire isformed in a wavy line shape containing at least one curve between theintersections.
 25. The conductive film according to claim 22, wherein atleast one of a pattern of the first thin metal wires and a pattern ofthe second thin metal wires is arranged such that one thin metal wirehas a smallest arrangement period number of the arcs, and thearrangement period number of the arcs is increased stepwise from the onethin metal wire to another thin metal wire arranged in one direction.26. The conductive film according to claim 22, wherein at least one of apattern of the first thin metal wires and a pattern of the second thinmetal wires is arranged such that two thin metal wires disposedadjacently on either side of a thin metal wire having a smallestarrangement period number of the arcs have approximately the samearrangement period numbers of the arcs, and two thin metal wiresdisposed adjacently on either side of a thin metal wire having a largestarrangement period number of the arcs have approximately the samearrangement period numbers of the arcs.
 27. The conductive filmaccording to claim 22, wherein the conductive portions have a crossingangle of approximately 90° in the intersections.
 28. The conductive filmaccording to claim 22, wherein the conductive portions contain ametallic silver portion formed by exposing and developing aphotosensitive silver salt layer disposed on a transparent support.